Rubber modified with tris-substituted resorcinol compounds

ABSTRACT

Novel rubber compositions having increased adhesion to fabrics and lower modulus value and the method of their preparation are disclosed. The addition of certain tris-substituted resorcinol compounds to rubber containing resorcinol, a resorcinol resin or other polymerizable reinforcing additive provides the abovedescribed properties.

United States Patent Alfred J. Kolka; Wun T. Tal; Roy H. Moult, all 01440 College Park Drive, Monroeville, Pa. 15146 lnvcntors Appl. No. 813,353

Filed Jan. 31, 1969 Division of Ser. No. 565,380, July 15, 1966, abandoned.

Patented Sept. 28, 1971 RUBBER MODIFIED WITH TRIS-SUBSTITUTED [56] References Cited UNlTED STATES PATENTS 3,304,222 2/1967 Wilken 156/335 X 3,410,818 11/1968 Yurcick et a1. 156/335 X 3,462,382 8/1969 Kolka et a1 260/3 3,242,118 3/1966 St. Clair 156/110 UX Primary ExaminerCarl D, Quarforth Assistant ExaminerStephen .l. Lechert, Jr. Attorneys-William G. Kratz, Jr. and Olin E. Williams ABSTRACT: Novel rubber compositions having increased adhesion to fabrics and lower modulus value and the method of their preparation are disclosed. The addition of certain trissubstituted resorcinol compounds to rubber containing resorcinol, a resorcinol resin or other polymerizable reinforcing additive provides the above-described properties.

RUBBER MODIFIED WITII TRISSUBSTITUTED RESORCINOL COMPOUNDS CROSS-REFERENCE TO RELATED APPLICATIONS This application is a division of application Ser. No. 565,380, filed July 15, 1966, now abandoned.

This invention relates to novel tris-substituted resorcinol compounds and their use in the modification of rubber compositions. More specifically, it relates to the addition of specific novel tris-substituted resorcinol compounds to a modified rubber composition for the purpose of improving the adhesion of rubber compositions to fabrics.

C. Danielson, US. Pat. No. 3,018,207 discloses that resorcinol or resorcinol resins when cured by means of methyleneaminoacetonitrile provided enhanced adhesion of a textile cord to the resulting rubber stock. Problems arise when such an amino compound is employed because of the toxicity of these amino compounds.

We have discovered certain novel tris-substituted resorcinol compounds which when added to rubber compositions containing resorcinol, a resorcinol resin or other polymerizable reinforcing additive, greatly increase the adhesion of the resulting rubber stocks to textile tire cords. In addition to the improved adhesion, the resulting rubber compositions have a lower modulus value than unmodified rubber. Since the modulus value is a measure of stiffness or lack of flexibility of rubber compounds, a decrease in modulos value provides for longer life of textile tire cords. R. Patterson and R. Anderson recognize in their article, Fatigue Failure in Nylon Reinforced Tires," Rubber Chemistry and Technology, Vol. 38, No. 4, Nov. 1965, that the stiffness of the region surrounding a cord influences significantly the fatiguing rate of the cord. In addition, the percent of elongation of these compositions is increased by the use of our tris-substituted resorcinol derivatives as curing agents.

The novel compounds of our invention are the tris-substituted resorcinol compounds characterized by the fonnula:

B CH CH R' wherein R is the same and selected from the group consisting of hydrogen and acetyl, and when R is hydrogen, R is lower alkoxy, and when R is acetyl, R is the acetoxy.

The compounds of our invention are novel compounds and are prepared resorcinol, paraformaldehyde and morpholine as starting materials.

The compounds of our invention are prepared by a process which 9 WEs i 9stwts 1 tbsiql qw ns J OH i 5 on, CH, H

(CH3C-O),O OH (EH l0 1 (N o j? 0- on: o I 0 u II on,- -ocrn CH,OCCH= I; O CCHs mow-0H.

0 0-ii-CH: l l E) 0H,i;-00H, -cH,o-c-cH,

O--CCH; (L i izno-o-ena R cH,ocH, 4211,0011,

; cmocm The general preparation of these compounds involves the reaction of 1 mole of resorcinol and 3 moles each of paraformaldehyde and morpholine in isopropanol at reflux temperature to produce tris(morpholino-methyl) resorcinol, the time of the reaction being about l'k hours. Utilizing the tris(morpholinomethyl) resorcinol as starting material, tris(acetoxymethyl) resorcinol diacetate can be produced by refluxing with excess acetic anhydride with exclusion of moisture. Alcoholysis tris(acetoxymethyl)resorcinol diacetatc is then employed to produce tris(alkoxymethyl) tris(alkoxymethyl) resorcinol.

All of these compounds have been found to have a beneficial effect upon reinforced rubber compositions. When employed in resorcinol or resorcinol-resin-modified rubber compositions these compounds act as a curing agent and cause the formation of unusual and exceptional physical properties in the resultant compositions.

The rubber component to which the reinforcing additive and any of the curing agents of our invention are added may be any of the various types of rubber substrates including natural rubber and synthetic rubbers such as styrene-butadiene rubbers, polybutadiene rubber, butyl-cthylenepropylene terpolymcrs, and the synthetic natural polyisoprenc rubbers. Reclaims of the above-mentioned rubber compositions are also used.

In addition to resorcinol, and resorcinol-aldehyde resins as the polymerizable reinforcing additive, other metadisubstituted benzene compounds containing hydroxyl or amino radicals may be used, as may be polyhydroxydiphenyls, polyhydroxynaphthalenes such as 1,5-naphthalendiol, and suitable polymerizable alkylated phenols, as for example 3,5- xylenol.

Q ifiriiiiiEiT iiiiifi mve rubbercompositions of our in vention, the resorcinol resin or other reinforcing agent is intimately mixed with the rubber hydrocarbon constituents in an intensive mixer such as a Banbury mixer, or by means of milling rolls or the like. Although, the tris-substituted resorcinol compounds, such as 2,4,6-tris(methoxyrnethul) resorcinol, may be mixed in at this stage of the processing, better results are generally obtained when these derivatives are added during the final mixing with the normal curing agents (sulfur and accelerators) on the milling rolls, and at lower temperatures. Mixing for longer times or at higher temperatures is not generally advantageous or deleterious to the product. The fact that these curing agents can be added at higher temperatures results in easierprocessing the modified rubber compositions and is advantageous over other curing agents which tend to precure and results in scorching.

The preferred amount of resorcinol, resorcinol-formaldehyde resin, or other polymerizable reinforcing additive added to the rubber stock is in the order of two parts by weight for each 100 part of the hydrocarbon-type rubber components (i.e. the total of the raw material rubber and synthetic rubber) in the rubber composition. The use of twice as much or onehalf as much of the polymerizable reinforcing additive also has a beneficial effect upon the rubber composition, but the properties are less than optimum.

The tris( methoxymethyl) resorcinol or tris(acetoxymethyl)- resorcinol diacetate is added in amount of about parts per l00 parts of resorcinol, resorcinol resin or other polymerizable reinforcing additive. An increase of the amount to about 50 parts per 100 parts of resorcinol or other resin did not result in any substantial improvements in the properties of the resulting compositions.

The modified rubber compositions of our invention show enhanced adhesion and physical property modification with textile tire cords such as rayon or other synthetic fibers such as nylon and polyester fibers. Enhanced adhesion is also provided with other tire cords such as glass fiber or metal cords.

The H-test has been employed by the rubber industry to determine the static adhesion of textile tire cords to rubber. This test is specified as ASTM D2l3862-T and was employed in testing the adhesion of the rubber compositions of this invention. The higher the l'l-test value, the stronger the adhesion of the rubber coating to the cord.

In the physical testing of the rubber compositions of our invention, the material was sheeted out at 45 mils thickness and was molded in standard ASTM slabs according to Method ASTM D-lS.

These slabs were cured at 293 F. for periods of 30 and 45 minutes. The tensile strength, modulus at 300 percent stretch, elongation at break, and set at break were determined according to ASTM D-4l2-62-T. The hardness of the composition was determined using a Shore-A testing meter, according to ASTM D-676-59T.

Our invention is further illustrated by the following examples wherein, unless otherwise denoted, parts are parts by weight.

EXAMPLE 1 THe 2,4,6-tris(morphorlinomethyl)resorcinal was made by forming a mixture of 3 moles of paraforrnaldehyde (9 parts), 3 moles of morpholine (26 parts) and 16 parts of isopropanol (as solvent). The mixture was heated in a steam bath until a humogenous solution resulted. Thereafter, l mole of resorclnul (ll parts) in 40 parts of isopropanol (as solvent) was added and the resultant solution refluxed in a steam bath for 1.5 hours. The hot solution was then concentrated on a rotary evaporator at about 60ll5 mm. and finally at about 6012 mm. The glassy residue was washed with ether to give a white solid (mp l32l35).

EXAMPLE ll Crude F l32 l35, (example I) 8.14 g., 20.0 moles was added to 20 ml. of acetic anhydrids and heated with exclusion of atmospheric moisture and with occasional shaking in a steam bath for hours. The solution was concentrated on a rotary evaporator at about 80] 10 mm. At the end of the concentration acetic acid odor was no longer detectable. The residue, 13.0 g. was taken up in [00 ml. of ethyl ether and washed with brine (3X30 ml.) and dried over magnesium sulfate. Evaporation of ether yielded 8.15 g. of yellow oil. The oil was dissolved in approximately ml. of absolute ethanol and crude 2,4,6- tris(acetoxymethyl) resorcinol diacetate, m.p. 68-70 C. was rer :ipitated by addition of approximately ZOO ml. of petrole um ether (b.p. 40-60). The weigh t of the crude product was i 5 5.9 g. pale yellow crystalline solid corresponding to a 72 percent yield. An analytical sample m.p. 72- 73.5 was prepared by recystallization of the crude product from charcoal-absolute ethanol, followed by methanol. The infrared spectrum of the crude product was identical to that of the analytical 2 v sample.

Analysis of the product by infrared and nuclear magnetic resonance (acetone-d,,) gave results consistent with the structure of 2,4,6tris-(acetoxymethyl) resorcinol diacetate. Elemental analysis results were: Clacd. as G i-[ ,0, (molecule 25 wt. 4l0.4) C, 55.60; H, 5.40; Found: C, 55.81, [1,559.

2,4,6-tris(rnorpholinomethyl) resorcinol mp.

, Zinc Oxide EXAMPLE Ill A rubber composition was formed containing the following ingredients:

Parts by wt.)

Styrene-butadiene rubber, Synpol lS5l (an oil extended type) Smoked Sheet No. IRSS (Standard quality natural rubber) Reclaim Rubber (Whole tire, first quality) Carbon black, Continex SRFIHM Octamine (Naugatuck) Stearic Acid Pine Tar (Tarene No. 40) Light Process Oil (Sunoco Circo Light) The above ingredients were mixed for 10 minutes in a Ban- I bury mixer, the temperature rising to about 320 F. during this period. The following ingredients were added when the master batch rubber was being milled on Farrel-Birmingham rolls at a temperature of 180 F.

Parts (by wt.)

Sulfur (Rubbermakers) Delac S Prills (Naugatuck) This composition was designated control."

EXAMPLE IV EXAMPLE V A composition was prepared using the ingredients and processing of composition A (example lV), except that tri nerie methyleneaminoacetonitrile (US. Pat.

3,018,207) was used in place of tris-(acetoxymethyl)resorcinol diacetate. This composition was designated composition B.

EXAMPLE VI The composition of examples [I], IV, and V were sheeted out at 45 mils thickness for physical tests and for adhesion evaluations. Comparison of the physical properties of the two modified rubber compositions and the control were made. Tensile strengths, modulus at 300 percent stretch, elongation at break, and set at break were determined according to ASTM D4l'2-62T. Hardness was determined using a Shore- A testing meter, according to ASTM D-676-59-T. The results were:

As can be seen, the composition A, containing tris(acetoxymethyl) resorcinol diacetate, exhibited improved properties including a decreased modulus value.

EXAMPLE Vll The rubber compositions of examples III, IV and V were also compared with respect to static adhesion according to ASTM D-2l38-62-T. Tire cord, Du Pont nylon type 714 of 840 denier, 2-ply, with 12/12 twist, was treated with a standard laboratory latex dip of the following formula:

Weight, grams Resorcinol-formaldehyde resins (75% solids, aqueous solution) 26.7 Water 407.7 Formaldehyde, methanol free (37%) 20.3 Aqueous NsOH Solution (l0%) 8.0 Vinylpyridine Latex (42% solid) (Gen-Tao) 250.0

The nylon cord was treated with low tension thru the dip (40-80grams), then dried at 430 F. at 119 feet per minute, an exposure time of 19.8 seconds.

Samples of this cord were vulcanized at 293 F. for 45 minutes to provide V4 inch H-test specimens. The results of static adhesion tests were:

control composition A composition B H-test (2l2 F.) [8.3 l9.2 20.8

As can be seen from the above data, the resorcinol resin modified rubber composition cured with tris(acetoxymcthyl) resorcinol diacetate exhibited good static adhesion.

EXAMPLE Vlll 2,4,6-tris(acetoxymethyl) resorcinol diacetate (prepared as in example ll), m.p. 6870 410 mg. 1.00 moles was added to 50 ml. of methanol. Concentrated HCl, 3 drops, was added and the solution refluxed in a steam bath under N for 3 hours. The solution was saturated with solid sodium bicarbonate and allowed to stand until the solution was very slightly yellow. The solution was filtcred and the filtrate concentrated on a rotary evaporator at -l0 to -5/water aspirator vacuum. The residue, a pink solid, 620 mg. was agitated with 10 mil. of benzene. Petroleum ether (b.p. 3060), 40 ml. was added and the mixture filtered. The filtrate was concentrated ona rotary evaporator at -l0 to room temperature and at 4 to l5 mm. The residue, colorless needles, mp. 5l52.5, 2,4,6- tris(methoxymcthyl) resorcinol, weighted l'70mg. (yield 70.3 percent). Recrystallization twice from petroleum ether, (b.p. 30-60) raised the m.p. to 5353.5.

The product was analyzed by infrared and by nuclear magnetic resonance (CDCl and the results were consistent with the structure of 2,3,6-tris(methoxymethyl) resorcinol. Elemental analysis results were: Calculated at C, H, 0,,; C, 59.48; H, 7.49; values found C, 59.38, H, 7.60. Molecular weight analysis by vapor-phase osmometry (in benzene) gave a value of 250 corresponding to the calculated value of24'2.3.

In a subsequent run a ten-fold scaled-up reaction was run. The diacetate solution was refluxed for 3 hours and subsequent concentrations of the reaction performed at l835 /water aspirator vacuum. 16 was comparable to the y SlllallCl' I'Ul'l.

EXAMPLE IX A rubber composition was prepared as in example lV, except that tris(methoxymethyl) resorcinol (example Vlll) was used in place of tris(acetoxymethyl) resorcinol diacetate. The physical properties of the resulting rubber composition (ascertained as in example Vl) were:

Cured at 293 F.

The composition was tested for static adhesion properties, employing the adhesive dip and conditions of example Vlll. The resulting H-test value, using a inch specimen at 212 F. (cured at 293 F. for 45 minutes) was 20.8.

EXAMPLE X A rubber vulcanizeable was formed according to example lV, except that resorcinol was used in place of the resorcinolformaldehyde resin. Testing of the physical properties as in example VI and adhesive properties as in example Vlll showed the composition to have properties comparable to those of composition A.

What is claimed is:

l. A vulcanizable rubber composition for adhesion to tire cord comprising rubber, 0.5 to 3.0 parts per parts of said rubber of a polymerizable reinforcing additive selected from the group consisting of resorcinol, a resorcinol-aldehyde resin, a polyhydroxynaphthalene, polyhydroxydiphenyls, alkylated phenols, and mctadisubstituted benzenes containing hydroxy or amino groups therein, and 5 to 20 parts per lOO parts of said polymerizable reinforcing additive of a compound of the formula:

alkylated phenols, and metadisubstituted benzenes containing hydroxy or amino groups to form a mixture thereof: and

b. adding to said mixture in an amount of 5 to 50 parts per parts of said polymerizable reinforcing additive a compound of the formula:

(-IIQR wherein R is the same and selected from the group consisting of hydrogen and aeetyl, and when R is hydrogen, R is lower ulkoxy, and when R is acetyl, R is acetoxy. 

2. Method of imparting increased adhesion properties to rubber comprising: a. adding to said rubber about 0.5 to 3.0 parts of a polymerizable reinforcing additive selected from the group consisting of resorcinol, a resorcinol-aldehyde resin, a polyhydroxynaphthalene, polyhydroxydiphenyls, alkylated phenols, and metadisubstituted benzenes containing hydroxy or amino groups to form a mixture thereof: and b. adding to said mixture in an amount of 5 to 50 parts per 100 parts of said polymerizable reinforcing additive a compound of the formula: 